To satisfy the fast growing demands from mobile internet market for higher data rate on wireless communication systems, many advanced technologies for increasing the data throughput have been put into use. Among them, Multiple Input Multiple Output (MIMO) data accessing scheme, a proven technology to effectively use the multi path environment, has been becoming a compulsory option in today's wireless communication systems both in base stations and mobile terminals.
Due to an inevitable strong electromagnetic wave mutual coupling between closely spaced antennas in a MIMO wireless terminal, such as a 4G LTE smart phone, the mutual coupling and spatial correlation between antennas are severely high, which lowers the channel capacity gain due to a strong signal correlation. Therefore, how to reduce the unwanted mutual couplings of coupled antennas is a very important issue.
U.S. Ser. No. 13/691,227 by Wu et al. proposed a new technique named Coupled Resonator Decoupling Network (CRDN) for decoupling two coupled antennas. The basic principle underlying is to design a second or higher order coupled resonator network that is connected to the two coupled antennas in parallel and is with its mutual admittance opposite to that of the two coupled antennas such that the unwanted mutual coupling of two antennas can be canceled in a relatively wide frequency band.
However, to apply the new technology in a mobile terminal, a small form factor integrated decoupling apparatus that is independent to the form factors of the antennas is highly desirable. In addition, the circuitry of using the integrated CRDN is also critical in applying the unique technology.